Pollution Induced Morphological Shift in Hemocytes of Aquatic Snail Bellamya bengalensis (Mollusca: Gastropoda) of Jalangi River in Tehatta, Nadia, West Bengal, India

Abstract

Molluscan haemocytes are circulating immune cells that can respond to environmental stress and may serve as cellular indicators of aquatic pollution. This study evaluated pollution-associated morphological and functional changes in the haemocytes of the freshwater snail Bellamya bengalensis collected from the Jalangi River at Tehatta, West Bengal. Specimens were manually collected from site A, which was less associated with human habitation, effluents, and agricultural runoff, and from site B, which was associated with wastewater discharge, agricultural runoff, domestic sewage, idol immersion, and bathing of domestic animals. Haemolymph was collected, and haemocytes were examined using Giemsa, Janus Green B, and trypan blue staining. Cell counts were performed using a haemocytometer, and viability was assessed by the trypan blue assay. Haemocytes from site B showed nuclear degeneration, membrane rupture, increased numbers of pyknotic cells, and reduced Janus Green B staining associated with mitochondrial condition compared with site A. The number of trypan blue-positive dead cells was significantly higher at site B, whereas cell aggregation on glass slides was significantly reduced. These responses indicate site-associated cellular stress and possible impairment of immune-related functions such as microaggregation. Because individual pollutants were not measured concurrently, the observed haemocyte responses should be interpreted as integrated indicators of environmental stress rather than effects attributable to a specific contaminant. The findings support haemocyte morphology, mitochondrial condition, viability, and aggregation as complementary endpoints for freshwater biomonitoring.